Tuning mechanism



Aug. 9, 1949. E. LAscHENsKl TUNING MECHANISM 2 Sheets-Sheet l Fild Nov. 17', 1948 J. E. LASCHENSKI Aug. 9,1949.

n TUNING MECHANISM 2, Sheets-Sheet 2 Filed Nov. 1'7, 1948 M .WQ

Patented Aug. 9, 15949 2,478,287 TUNING MECHANISM Joseph E. Laschenski, Springfield, Pa., assignor to PhilcoCorporation, poration of Pennsylva Philadelphia, Pa., a cornia Application November 17, 1948, Serial No. 60,467 4 Claims. (Cl. 'M -10.8)

This invention has to do with control mechanism for electrical apparatus. While of broader utility, the invention has particular applicabill ity' to radio tuning apparatus.

Many present-day tuning devices usedk with radio receivers are'of the type including socalled inductance tuning, and employ a movable carriage, or core bar, adapted to` position the cores of a plurality of inductors in response to adjustment in the position of the core bar. Although the principles of the invention, in its broader aspect, may be applied to control mechanism and tuners other than `those of the inductance type, the apparatus of the invention is particularly advantageous when used with tuners of the aforesaid type and the invention will, therefore, be illustrated and described as embodied in such a tuner.

As will be recognized by those skilled in the art to which the present invention appertains,

tuners of the class concerned commonly include an elongate movable carriage to which the aforesaid core members are connected, the coremembers engaging the carriage, or core bar, at points spaced along the latter. In order that the apparatus may have the desired accuracy inl the tuning operation, it is necessary that the core bar move with purely rectilinear motion and that all cocking -or twisting movements of the core bar be prevented. Further, lost motion and backlash in the driving mechanism must be substantially eliminated. Attempts have been made to meet these requirements by the provision of a, tuning mechanism'utilizing precisely machined gear drives for the core bar, accurately manufactured and aligned guide rod arrangements for mounting the core bar, and the like. Evidently such expedients involve expense and complexity too great to meet the requirements established by mass production methods.

With the foregoing in mind, it is an important object of the present invention to provide a tuning device in which the carriage or bar which.

drives the frequency-determining elements moves with true rectilinear motion, and in which such movement may be `attained by the use of apparatus of an extremely simple and inexpensive nature.

An outstanding feature of the invention resides in the provision of tuning apparatus in which movements of the core bar are effected with a negligible degree of backlash, lost motion, reset error, and the like, and which apparatus is characterized by unusual simplicity in assembly. 'I'he invention is also characterized in 2 that highly satisfactory embodiments thereof may be manufactured without resort to critical and expensive tooling.

The invention extends further to certain novel constructional features and arrangements hereinafter described, and illustrated in the accompanying drawings, in which: f

Figure 1 is a view, in perspective, of a tuning mechanism embodying the present invention;

Figure 2 is a'sectional view, taken in the direction indicated by the line 2 2, of Figure 1; and

Figure 3 is an exploded, perspective view illustrative of the inherent simplicity of the apparatus and the ease with which it may be assembled.

First making brief reference to the apparatus, the illustrated embodiment comprises a multicoil inductance tuner having a single movable carriage, or core bar, to which the core members of the tuner are secured. This carriage is mounted forI reciprocatory movements, whereby to vary the frequency-determining position of the inductance cores, such movements being effected in response to rotation of a suitable manual control element. As will appear more fully in what follows. these movements are rectilinear in nature, the apparatus being such as to prevent any cocking movements of the core bar, as well as any backlash, end play, or the like, with .the result that misadjustment of the associatas will later appear, se'rve to mount simple and novel apparatus effective to drive the aforesaid core bar. A back wall I3 provides support for the adjustable inductors indicated at I 4, I5 and I6. These inductors comprise coil and core assemblies of conventional type, each said assembly having associated therewith a core, of iinely comminuted iron, or the like. The. cores appear at I 4a, I5a and Ilia, in Figure 1, and each car-4 ries a mounting rod (see Mb, I5b and Ilib) which rods extend into threaded engagement with the core bar designated, generally, at I1. As thus far described the mechanism is more or less conventional in nature, and reference will now be inadeto the novel manner in which the core bar, and the driving elements therefor, are mounted within the tuning apparatus.

The core bar is generally U-shaped, in plan, and each of the leg portions thereof is configured to provide a rack, these racks appearing to good advantage at I8 and I9, in Figure 3. The right end of the core .bar (as seen in Figures 1 and 3) has extending therefrom a pair of lugs or guides and 2I adapted to be received within a slot 22 provided in side wall II, thus securely positioning that end of the core bar against movements in the vertical sense. More detailed reference will be made, hereinafter, to the manner in which the lugs 20, 2| cooperate with the slot 22, during the assembly operation.

1n order to effect the above-mentioned rectilinear movements of said core bar, during the tuning operation, driving interconnections are provided which are of lsuch a nature that the driving motion imparted to one end portion of the core bar is transmitted to and also applied to the ODPOSite end of said bar. Thus, in effect, uniform driving motion is imparted to both end portions of the core bar. To this end,V it is to be noted that each of the side walls II and -I2 is provided with an aperture providing a slot extending transversely oi the direction of reciprocatory movements of the core bar. These slots are shown at 23 and 24 (Figure 3) and journalled within said slots is a cross rod 25 carrying a pair of pinions 26-26, which are disposed at opposite ends of said rod. As best appears from Figures 1 and 2, the cross rod 26 is received within the aforesaid slots 23 and 24 and maintained in such position that the pinions 26--28 are disposed to engage the overlying racks `provided upon the core bar.

Driving motion is imparted to the carriage through the agency of a rotatable element 21 which comprises a lead screw for said core bar and further serves to secure the left end of said bar against displacement movements in the vertical sense. The outer end of said rotatable element is journalled in an apertured tab 28 extending upwardly from the base plate I0, and its inner end extends through an aperture 29 provided in the rear wall I3.

The left-hand leg portion of the U-shaped core bar I1 terminates in a Wall 30 provided with a. central circular aperture 3I (Figure 3) and a pair of oppositely disposed elongated apertures 32-32. The forward portion of the carriage is apertured as at 33 and, as will now be under` stood, the rotatable element or lead screw may be introduced through the aperture 33, after which it is moved inwardly 'of the apparatus until the threaded portion thereof passes through aperture 3l and, nnally, is received within the aperture shown at 29. The aperture 3| is of a size to make threaded driven engagement with lead screw 21 and it will therefore be clear that rotary movements imparted to said lead screw result in reciprocatory movement of the core bar I1. Clearance must be provided between element 21 and the walls which dene apertures 28, 29 and 33. As will be readily understood, even very small tolerances at these points, for example of the order of one-thousandth of an inch, are su'icient to permit several thousandths of an inch displacement of the right-hand end portion of the core bar. Displacement movements of this order will introduce objectionable mistuning of the circuits controlled by the cores.

To eliminate any backlash which might otherwise occur between the surfaces of aperture 8l and the threads of the lead screw,v core bar I1 is provided with a pressure element or plate 34 having a pair of tongue portions 35-35 which are slidingly received within the apertures 32-32. A spring bears against wall 38 and the surface of plate 34 and, since lead screw 21 passes through said plate* in threaded engagement with the latter, the spring 36 reacts between oppositely facing surfaces of the lead screw, and thus eliminatesV lost motion or backlash between lead screw 21 and the core bar. A bifurcated, resilient member 31 straddles the rear wall I3, and is provided with an aperture disposed in alignment with the aperture 29. The rear leg portion of this member serves as a thrust bearing for the lead screw 21 and thus contributes to the lack of end play in the apparatus and the resultant accuracy in operation.

As thus far described, it will be clear that rotary movements imparted to the element or lead screw 21 result-through the inter-engagement of aperture 3| and said lead screw 21-in the application of driving force to the core bar I1. In further accordance with the present invention, such driving movements are also imparted to the opposite end of the core bar through the agency of the aforementioned cross rod 25 and the associated rack and pinion devices.

As above set forth, the cross rod is retained captive within the sl-ots 23, 24 and, as clearly appears in Figures 1 and 2, the driving movements imparted to the core bar result in reciprocation of the rack I8 with respect to the underlying pinion 26. In this manner rotation of the cross rod is effected and similar movement is imparted to the opposite rack I9 through its associated pinion. It is particularly `to be noted that if, by way of example, the driving movement imparted to the core bar is suicient to move the rack I8 a K distance such that the underlying pinion is driven through 360 degrees, the oppositely disposed pinion will also move through 360 degrees and thus impart driving force to the rack I9 suiicient to insure movement of the latter rack a distance equivalent to the movement imparted to rack I8-through the lead screw 21.

A pair of spring elements, shown at 38 and 39, are provided, each of which elements has a bearing portion (38a and 39a) which bears against the under side of cross rod 25-at the region of each end thereof-and resiliently reacts against a pair of lugs struck up from the plane of each of the walls II and I2. Such lugs are shown at 40-40, with reference to wall I2, and at III-4I, with reference to the oppositely disposed wall I I.

As will clearly appear from the following description of the manner in which the apparatus is assembled, the spring elements 38 and 39, the aforesaid lugs, and the slots 23 and 24 cooperate in such manner as not only to eliminate all backlash which would otherwise be present between the rack and pinion elements, but also contribute largely to the unusual ease with which the apparatus may be assembled,

Now making reference to the exploded, perspective showings of Figure 3it will be understood that the initial step in the assembly operation is to introduce one of the pinions 26 through an aperture 42, formed in end wall I 2, after which the cross rod 25 is moved transversely of the end plate Ill until one end portion thereof is received within slot 23. When this position is reached, the pinions lie just inwardly of the adjacent end walls and the left end of the cross rod, as viewed in Figure 3, may be lowered until said left end is journalled within slot 2l.

The carriage il is then introduced between the end walls Ii and I2 with its right-hand portion angled downwardly in such manner that lugs and 2| are received within the slot 22 provided in end wall Il. Thereafter the left end of the core bar is lowered to bring aperture 33 into alignment with the aperture formed in tab 28, in which position the lead screw 21 is inserted through these aligned apertures, Continued inward movement of the lead screw causes it to pass through the apertures provided in wall and plate 34 and, ilnally, to become Journalled in aperture 29, in which iinal position its inner end portion engages the thrust`-bearing member 81.

The assembly operation is completed by engaging the bearing portions 38a and ae-of the spring elements I8 and 39-with the opposite ends of the cross rod 25 and flexing the i'ree ends of each spring element upwardly until they snap downwardly into the slots provided by the aforesaid lugs 40-40 and li-ll. When thus positioned, spring elements 38 and 39 resiliently urge the cross rod 2l upwardly, and maintain it in position such that the pinions 26-2l are in positive driving engagement with the overlying racks.

I claim:

1. In a tuning mechanism, bed plate structure, a carriage mounted upon said structure with freedom for reciprocatory movements with respect thereto, means for imparting driving motion to one portion of said carriage, gear means Journalled in said structure and disposed for driving engagement with a portion of said carriage spaced from said portion rst mentioned, said gear means being responsive to movement oi* said carriage to impart to said second-mentioned portion driving motion equal' to that motion inparted to the portion ilrst mentioned, and resilient means urging said gear means into the stated driving engagement.

2. In a tuning mechanism, framing including a pair of spaced generally parallel flanges each including a guideway, a cross-shaft extending between said flanges andI having end portions freely receivable within and withdrawable from said guideways, a carriage mounted for sliding movements between and in parallelism with said flanges, rack means carried by said carriage, gear means carried by said cross-shaft and disposed for meshing engagement with said rack means, and spring means reacting between said flanges and said cross-shaft to urge said cross-shaft to move in said guideways and into meshing engagement with said rack means.

3. In an adjustable mechanism. framing including a pair oi. spaced generally parallel iianges, said anges being provided with confronting apertures comprising journal portions, rotatable shafting spanning the distance between said danses and having oppite and normally received within said Journal portions, a pair of gears carried by said shafting and each disposed thereon adjacent an associated one of said anges when said shafting occupies the said normal position, a carriage removably mounted within said framing for sliding movement between and in parallelism with said flanges, said carriage having a pair of rack portions each of which is normally disposed in meshing engagement with an associated one of said gears, said framing being apertured to provide for ready insertion of said shafting within said framing and withdrawal of said shafting therefrom, the aperture last `mentioned being so disposed as to provide for such insertion and withdrawal movements upon removal of said carriage from said framing, and resilient means cooperable with said journal portions to maintain `said gears in meshing engagement with said racks.

4. In a tuning mechanism, framing including a pair of spaced generally parallel ange por-4 tions each of which is provided with an aperture. movable carriage means mounted in said framing and including a pair ot spaced wall portions, said carriage means being adapted to make driving engagement with an adjustable frequencydetermining device, lead screw means iournalled in said framing and coupled to one portion of said carriage means to impart driving motion to said portion. said lead screw means being selectively operable to `impart driving motion to said portion in two different senses thus selectively to impart to said carriage means movements in opposite directions, a pair of racks each of which is carried by an associated one of said spaced wall portions, a pair of pinions iixedly secured upon common rotatable shafting and each of which pinions is disposed for meshing engagement with an associated one of said racks, said shafting being journalled within the apertures provided in said flange portions and the construction and arrangement being such as to provide for free and unobstructed introduction of said shafting within said apertures in a position such that said pinions lie inwardly of said ilange portions and bear thereagainst, and a pair of spring elements, each of said spring elements being mounted upon an associated one of said ilange portions and reacting between the associated flange portion and said shafting to urge said pinions into the stated meshing engagement with said racks.

' JOSEPH E. LASCHENSKI.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

